I think that is a very useful website for quick reference. However, I know of other sites with better tutorials. One I would recommend is:
http://webmonkey.com/
If you don't know which languages are best to learn, I would recommend starting with HTML and XHTML, then CSS, then PHP. If you want, you could go back to JavaScript. The rest are additional languages that you can use for certain things, but the ones I mentioned cover just about everything you would need to do.